Biologically active substances in nutrition are physiologically important components. They can have the most varied functions in the organism and as a result make a positive contribution to health. Biologically active substances can act, for example, as classical nutrients, can stimulate immune activity or have protective activity or intervene in physiological processes in the body. Biologically active substances can include, inter alia, probiotic microorganisms, prebiotic substances, nutrients or secondary plant constituents. Enrichment of the diet with components of this type in a stable and in particular bioavailable form is therefore desirable from the nutritional aspect.
Dietary fibers are a heterogeneous product group. Many dietary fiber preparations are based on plant fibers and consist predominantly of water-insoluble polysaccharides in addition to pectin, lignin and plant gums (for example wheat fibers, oat dietary fibers, rice dietary fibers, apple fibers, citrus dietary fibers etc.). In addition there are also soluble dietary fibers which are mostly made up of complex carbohydrates (for example fructo- or galactooligosaccharides, β-glucans etc.). Dietary fibers taken in via the diet are distinguished by the fact that they are indigestible constituents for humans. Because of their inert character, dietary fibers reside in the intestine and can there optimally exert their physiological effects, for example increasing intestinal peristalsis, effects on cholesterol absorption, prebiotic activities etc. An increased intake of dietary fibers is desirable for nutritional reasons. A daily intake of 25-30 g of dietary fiber is recommended by nutritionists.
For the reasons described it is expedient to provide dietary fibers and biologically active substances in a stable and nutritionally utilizable form via the diet or other delivery route to the organism. An optimal release of the biologically active substances, for the reasons described above, is not desirable until after passage through the stomach in the lower digestive tract. Furthermore, it is desirable that adverse sensory perceptions of nutritionally valuable substances in foods do not occur. This is, in the case of insoluble dietary fibers, frequently a marked sensory perception of particles in the food matrix (“scratchy off-taste”).
The technique of microencapsulation has long been used commercially predominantly in the pharmaceutical industry. For some time, however, there have also been studies on the use of encapsulation in food technology (Jackson, Lee, 1991, Kanawija et al. 1992, Hegenbart, 1993, Arshady, 1993, Dewettinck, 1997, Pegg, Shahidi, 1999). The spray-drying process is one of the most frequently used processes for encapsulating various substances in the food industry. It can be considered as one of the essential advantages here that spray-drying is suitable for processing heat-sensitive materials. In addition, the process is inexpensive and offers the advantage that an existing technology can be utilized. In order to make possible targeted utilization for the various application sectors in the food industry, studies of the customary materials in different combinations would have to be carried out, since single materials cannot comply with the complex requirements which a food makes of the capsule material. Studies to date were concerned predominantly with decreasing the volatility of substances and their oxidation by embedding them into a suitable material. The effects resulting from the physicochemical properties of the capsule materials and of the physical conditions of this process require further study (Ré, M. I., Drying Technology, 1998, 16(6), 1195-1236).
Most patents or patent applications relate to fields of application in the pharmaceutical industry. The major roles are taken here by the capsule materials used (generally in combination with specific activities or effects), the controlled release of substances via the application of the encapsulating technique and the stabilization of substances. In the food sector there are far fewer patents, which, however, are essentially determined by these three directions. In the case of microencapsulation of cells or cell free extracts (CFE), physiological stability in combination with their use as a pharmaceutical product play the major roles.
Microencapsulation with the purposes of a) use of dietary fibers, in particular fibers as a support material for biologically active substances, in particular microorganisms with simultaneous increase of the nutritional value, b) support material/microorganism interactions, c) prevention of support material/capsule material interactions, d) stabilization of the biologically active substances in the product and in the food with correspondingly extended shelf life, has not been described to date.
Immobilization of lactococcus, which are less sensitive than lactobacillus species, is possible in a matrix made of alginate/polyamino acids. In this experiment a study was to be made as to what extent the stabilization, handling and storage of microorganisms may be improved by the immobilization. Lactic acid production, as an indicator of metabolic activity, was reduced, however, after handling and storage of the microorganisms in comparison with microorganisms which had not been embedded. No information was provided, however, on interactions of the capsule material with its direct environmental surroundings (for example foods) or with the microorganisms or the use of support materials (Larisch, B. C., Poncelet, D., Champagne, C. P., Neufeld, R. J., J. Microenc., 1994, Vol. 11, No. 2, 189-195).
The encapsulation of lactic acid bacteria of the genera Streptococcus, Lactobacillus, Pediococcus, has also been achieved in various materials using extrusion. In this case a study was made of the viability of the encapsulated organisms in acidic media simulating the gastrointestinal tract and of the shelf life and stability of the encapsulated microorganisms at various temperatures. It was found in this case that the survival rates depend on the physicochemical properties of the capsule materials. The shelf-life studies at different temperatures found increased survival rates of the encapsulated organisms at temperatures above 22° C. in comparison with the unencapsulated bacteria. No statements were made about metabolic performance and/or metabolic activity. (Kim, H. S., Kamara, B. J., Good, I. C., Enders Jr., G. L., J. Indust. Microbiol., 1988, 3, 253-257).
Encapsulation techniques for lactic acid bacteria are also described in various patents. WO-A 9716077 refers to probiotic formulations which can be used as food ingredients. In this case the microorganisms are mixed with a second substance as carrier or shell substance, which in the latter case leads to an improved stability to passage through the stomach. Production processes for formulations to increase the stability of such probiotic microorganisms in the gastrointestinal tract are also described in CN-A 1113515, CN-A 1124773, WO-A 9920745 or WO-A 9952511. In these cases, especially, encapsulation techniques are used in order to protect the microorganisms against gastric acid. A disadvantage of these processes is that the resultant formulations are not stable in most food applications.
WO-A 9608261, WO-A 9734615 and WO-A 9734592 describe the microencapsulation of probiotic microorganisms with modified and unmodified starches. In these cases the starch acts as transport medium for the probiotic microorganisms into the stomach. WO-A 9826787 describes a method in which improved passage through the gastrointestinal tract for probiotic microorganisms is achieved using β-glucan as support.
The spray-drying process can also be used to increase the stability and storage life of bacteria. Thus in the agricultural field, in the case of seed material, by spray-drying a strain of rhizobacteria, improved preservation and protection of the seed material against infection with disease and premature germination are achieved. Encapsulation was achieved using spray-drying with the use of various materials all of which except for one combination (modified starches) are not permitted for the food sector. (Amiet-Charpentier, C., Gadille, P., Digat, B., Benoit, J. P., J. Microenc., 1998, Vol. 15, No. 5, 639-659).
In the food sector, lactic acid bacteria were also stabilized via various drying processes. Thus WO-A 9957242 describes a process which gives preparations suitable for foods made from lactic acid bacteria with additional carbon-dioxide-generating additives via various drying processes. Increased stability of encapsulated microorganisms was demonstrated when algal polysaccharides were used as capsule material. In this case the aerobic microorganisms were embedded into the capsule material by crosslinking. The resultant microorganisms can be used in the environmental sector and displayed similarly good performance with respect to PCP degradation as non-embedded microorganisms. (Hammill, T. B., Crawford, R. L., Can. J. Microbiol., 1997, 43, 1091-1095).
A disadvantage of the above described processes and substances is that they are not stable in most food applications. When in particular microorganisms are added to foods, the resulting survival rates of the microorganisms are still too low to develop nutritional effects. Furthermore, with many biologically active formulations, adverse sensory perceptions occur. In addition, it is disadvantageous that the biologically active formulations, although they can pass to their destination (intestine), because of the pH, they cannot fully develop their activity there.
The object of the present invention was therefore to provide a system which simultaneously                prevents an interaction with the surrounding food (for example in some cases prevents unwanted swelling properties of the dietary fibers)        provides nutritionally valuable substances without adverse sensory perceptions,        ensures increased storage stability of nutritionally valuable substances and        optimizes the quantitative supply and localization of release of the biologically active substances at the desired site (optimized bioavailability).        